The present invention provides a nylon composition incorporating an additive that is not soluble in the nylon, which has improved toughness over the compositions of the prior art.
It has become common in the art to provide a nylon polymer with improved properties by incorporating therein certain additives that are insoluble in the polymer (The term "insoluble" as used herein indicates that the insoluble additive is present in the polymer in the form of discrete agglomerates visible in a photomicrograph of the composition and is capable of separation from the polymer by solution of the polymer in a suitable solvent and filtration of the additive from the resulting solution.) Thus, flame retardance is commonly obtained by addition of halogen-containing compound and a metal or metal compound, strength is conferred by blending in a mineral filler. Pigments and talc are also frequently intimately dispersed in the polymer to improve appearance.
However, the incorporation of such additives commonly leads to embrittlement of the composition and this imposes severe use limitations on them. In such a situation the commonly used plasticizers for nylon are found to be ineffective as regards increasing toughness. In his book on "Industrial Plasticizers" (MacMillan, 1963) at p. 2, I. Mellan, states that the more highly polar a resin is, the more highly polar must be the plasticizer used in conjunction with the resin. Polyamides are known to be very highly polar and in the 1974-5 edition of Modern Plastics Encyclopedia (MPE) p. 248, Mellan's teaching is repeated in the statement that the polarity of the polymer and the plasticizer chosen should be roughly matched for good compatibility. On the same page of MPE aliphatic glycols and aromatic sulfonamides (both highly polar) are specified as being suitable plasticizers for nylon.
We have now discovered a class of plasticizers for nylon polymer compositions incorporating additives insoluble in the nylon, that not only increase the toughness of the composition in an unexpected and unpredictable fashion but in some cases actually improve the nylon properties in this respect on ageing.